Furthermore, the invention also relates to a method for identifying defects in a fuel injection system, with the fuel injection system including at least one high-pressure pump, at least one fuel accumulator, at least one fuel pressure control valve and at least one pressure sensor for recording the pressure prevailing in at least one fuel accumulator.
In addition, the invention relates to a vehicle with a device for identifying defects in a fuel injection system as well as a diagnostic unit with a device for identifying defects in a fuel injection system.
Fuel injection systems which are within the framework of this publication serve as the high-pressure injection of fuel into the cylinders of an internal combustion engine.
Such a fuel injection system may be equipped with a fuel accumulator which is filled with fuel using a high-pressure pump and is in this case brought to a pressure level required for the high-pressure injection. Fuel is fed to the high-pressure pump itself using a low-pressure fuel pump; said fuel drawn out of a fuel tank using a low-pressure fuel pump. Different measures can be taken in order to control or regulate the fuel injection system. Both mechanical regulators in the low-pressure area and control valves in the high-pressure area are known.
The latter is, in particular, of importance in connection with continuously operating high-pressure fuel pumps which feed the fuel into the fuel accumulator (the “rail”). Such fuel pressure control valves can be adjusted via a magnetic force which can be specified electrically.
Therefore, by and large, complex systems are being dealt with here in which different defects may occur. The fact that there is a defect can be seen in particular in a lower fuel pressure in the fuel accumulator—however, it is not possible to exactly locate the cause of defects only on the basis of this pressure which has been identified as being too low.
A method and a device for monitoring a fuel metering system of an internal combustion engine in which an output signal of a pressure sensor, which records the pressure in a fuel accumulator is filtered using a bandpass filter, is known from WO 01/83971. The bandpass filter is embodied in such a way that it filters out frequencies which correspond to the pump revolutions or integer multiples of the pump rotational speed. If the filtered output signal exceeds a threshold value then it is identified that there is a defect in a high-pressure pump or a pressure control valve.